The cricothyroid muscle after cricothyroidotomy. A porcine experimental study.

Cricothyroidotomy in elective use or emergency situations has been discussed by several authors during recent years. The main complication reported has been subglottic stenosis. We have used this method for several years and among our patients there has been no case of stenosis. The major complication in our material has been voice dysfunction. Some of the patients had a change in voice quality consistent with dysfunction in the cricothyroid muscles (diminished voice range and a lowered pitch). The aim of this study was to investigate whether cricothyroidotomy and insertion of a tracheostomy tube caused physiological or morphological changes in the cricothyroid muscle, by direct injury or secondary to a peripheral nerve lesion. In the six animals that were cricothyroidotomized during 7-9 days and examined after 9-15 weeks, we found neither changes in the EMG nor in the muscle morphology indicating injury to the muscle or its peripheral nerve supply.

Thoracic and abdominal lymph drainage in relation to mechanical ventilation and PEEP.

Thoracic and abdominal lymph flow have been studied in 25 dogs. Thoracic lymph flow (TLF) was found to be (mean +/- s.e. mean) 6.1 +/- 1.4 ml/h before, and 29 +/- 4.6 ml/h after the induction of lung damage with oleic acid. TLF was depressed by 50% both before and after lung damage, when a positive end-expiratory pressure (PEEP) of 1.0 kPa (10 cmH2O) was applied. This suggests impeded drainage of the lung tissue. Spontaneous breathing, compared to mechanical ventilation, significantly increased TLF by approximately 70%. Abdominal lymph flow increased from 61 +/- 5.3 ml/h to 111 +/- 12.6 ml/h, when a PEEP of 1.0 kPa was applied. These findings demonstrate that PEEP may contribute to oedema in a surgical area. It is concluded that increased intrathoracic pressure reduces TLF, and spontaneous breathing increases TLF, as compared to mechanical ventilation without PEEP.

Effects of prolonged surgical trauma on the extravascular lung water and central blood volume in the dog.

Extravascular lung water (EVLW) and central blood volume (CBV) were measured in 13 dogs with a double-indicator dilution technique (dye-cold), the indicators being detected intravascularly. Animals in a control group (n = 5) were mechanically ventilated for 8-15 h after baseline measurements. Another group of animals (n = 8) were subjected to extensive lymph duct cannulations, including a thoracoabdominal incision, and the dogs were followed for 8 to 18 h postoperatively. All dogs (n = 13) then received a dose of oleic acid intravenously in order to create lung damage. A positive fluid balance was maintained throughout the experiment. Basal EVLW was 8.8 ml/kg (n = 13) (similar in both groups), and did not change significantly in either group before oleic acid. Basal CBV was 18.5 ml/kg (n = 13); it increased (P less than 0.05) in the control group and decreased (P less than 0.05) in the surgery group during a 8-15-h period. EVLW was doubled (P less than 0.001) and CBV decreased slightly 2 h after oleic acid administration. The lung damage was similar in both groups, and was accompanied by increased pulmonary vascular pressures and marked reductions in arterial oxygen tension and thoracic compliance. The findings suggest that an earlier proposed dog model for the simultaneous measurement of EVLW and lymph flow can be used in long-term studies on lung fluid balance.